This patent application is associated with the materials cited in U.S. Pat. No. 5,312,790 granted on May 17, 1994, entitled "Novel Ceramic Ferroelectric Material", U.S. Pat. Ser. No. 08/207,446 filed Mar. 7, 1994 , and entitled "Novel Ceramic Ferroelectric Composite Material--BSTO-MgO", now U.S. Pat. No. 5,427,998; U.S. Pat. Ser. No. 08/207,447, filed Mar. 7, 1994 and entitled "Novel Ceramic Ferroelectric Composite Material--BSTO-ZrO.sub.2 ", now U.S. Pat. No. 5,486,491, and U.S. patent Ser. No. 08/215,877, filed Mar. 22, 1994 and entitled "Novel Ceramic Ferroelectrics for Phased Array Antennas". The present invention is specifically an expansion and improvement of the materials cited in the above-referenced U.S. Pat. No. 5,427,988, entitled, "Novel Ceramic Ferroelectric Composite Material--BSTO-MgO". These patent applications are commonly owned by the U.S. Government as represented by the Secretary of the Army.
A need exists for the fabrication of ceramic materials having improved electronic properties which may be adjusted for a particular, intended use. The present invention deals with novel ceramic ferroelectric materials having ideal properties for use, for example, in phased array antenna systems.
The ferroelectric materials are a replacement for the more expensive current driven ferrites which are currently used in phased array antennas. The invention outlines ferroelectric materials which provide adequate phase shift with a minimal insertion loss.
Current attempts to use ferroelectric materials employ porous ceramics, whose properties are less than ideal for their intended application. Porous ceramics of the Ba.sub.1-x Sr.sub.x TiO.sub.3 (BSTO) type are commonly employed in ceramic phase shifter antennas. However, these materials display certain deficiencies due to processing difficulties, cost and poor overall electronic and microwave properties. These deficiencies include electronic inhomogeneity, structural weakness, reproducibility, and large loss tangents.
Barium Strontium Titanate (BaTiO.sub.3 --SrTiO.sub.3), also referred to herein as BSTO, has been known to be used for its high dielectric constant (approximately ranging from 200 to 6,000) in various antenna applications. This is set forth by Richard W. Babbitt et al. in their publication, "Planar Microwave Electro-Optic Phase Shifters," Microwave Journal, Volume 35 (6), (June 1992). This publication concludes that there exists a need for additional research to be conducted in the materials art to yield materials having more desirable electronic properties.
Although the employ of BSTO in phase shifters is known, nowhere in the technical arena of ceramic arts has there been any suggestion of modifying BSTO, or combining BSTO with additives, in the manner described herein. Moreover, the specific BSTO combinations, which have enhanced electronic properties, are deemed novel.